This version was intended to be geocentric and used the GRS80 ellipsoid. Never before have we been able to estimate the ellipsoid with such precision because of the global set of measurements provided by GPS. Get your coordinates in the WGS84 on your display. WGS84 frames are specifically named NAD83 (CORS96) and WGS84 (G1150). However, because the geodetic datums were different, the resulting projected coordinates will also be different. The radio waves transmitted by GPS satellites enable extremely precise Earth measurements across continents and oceans. Download the free Excel template to perform the following operations: - Conversion of UTM Coordinates to Decimal Degrees. And even today, people continue to change geodetic datums to make them more accurate. - Conversion of Coordinates in Decimal Degrees to UTM. GIS: Convert NAD27 to WGS84 with programming function like PHP (2 Solutions!!) The Global Positioning System (GPS) references the World Geodetic System (WGS84) as its coordinate reference system. The input data is actually on the Old Hawaiian datum. DWalsh wrote: > > Hi Rod, > I was hoping to see a difference between the two layers, but I saw none. I would recommend proj4js. What the above-mentioned C source-code does is simply use the two data files as data arrays and offsets into them and interpolates between the 4 numbers that would be up-left, up-right, down-left, down-right from the location you want to convert. rev2023.3.3.43278. This results in more accurate geodetic datums over time. This effort, known as HARN or HPGN, is a cooperative project between the National Geodetic Survey and individual states. Nearly all published statements about the amount of shift between NAD27 and NAD83 are shifts measured in meters on unprojected (latitudelongitude) data. Newer realizations of NAD83, such as NAD83 (CORS96) and NAD83 (2011) can differ from NAD83 (1986) by a meter or so. Datum Transformations Converting Coordinates from NAD27 to NAD83, 25 Map Types: Brilliant Ideas to Build Unbeatable Maps, Ocean Currents Map: Visualize Our Oceans Movement, 3 Wildfire Maps: How to Track Real-Time Fires Around the World. Input the coordinates in a decimal degrees (DD) format. I don't need to be perfect. To get NAD83 to WGS84, input coordinates in NAD83 format into the fields, then click the Convert button. SPCS83 (Version 2.1) Converts NAD 83 State Plane Coordinates to NAD 83 geographic positions (latitudes and longitudes) and vice versa. Steps of transformation: I suspect the group that originated the app got bought out or has disbanded. Your email address will not be published. Converting a NAD27 Lambert Conformal Conic custom projection to WGS84 using QGIS. Learn more about Stack Overflow the company, and our products. What is the correct way to screw wall and ceiling drywalls? By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. Should I use the NADCON converter at http://www.ngs.noaa.gov/cgi-bin/nadcon.prl to convert my WGS84 coordinate data to NAD27? SPCS DEMs SPCS imagery All functionality are processed using Our APIs, which are being used by many Fortune 100 companies across 114 countries. All Rights Reserved. This compares to the Clarke ellipsoid with a semi-major axis of 6,378,206.4 m and a semi-minor axis of 6,356,583.8 meters. NAD 27 and NAD 83 provide a frame of reference for latitude and longitude locations on Earth. NAD_1927_To_NAD_1983_Alaska. The mapping platform for your organization, Free template maps and apps for your industry. Cartisan Map Coordinate Converter: Enter latitude and longitude in separate columns for degrees, minutes and seconds, and have them converted to a DD MM SS string, DD MM.d string, or numeric decimal degrees. En este ejemplo, yo tengo un mapa en NAD27, entonces elegimos este sistema en el botn select coordinate system; este deseo pasarlo a NAD83, este se lo asigno en el siguiente botn del mismo panel (source drawing). I tried in gdal, How Intuit democratizes AI development across teams through reusability. convert nad27 to wgs84 formula. The best answers are voted up and rise to the top, Not the answer you're looking for? A number of methods have been proposed for performing the datum adjustment. NAD 27 and NAD 83 provide a frame of reference for latitude and longitude locations on Earth. - YouTube GIS: Convert NAD27 to WGS84 with programming function like PHPHelpful? Proj4php is an OSGeo community project. Or convert them to any other coordinate I can map onto tableau. or, depending upon your platform, you may use stdin/stdout redirection as follows. We are not lost, we just don't know where we are.. You can post now and register later. National Spatial Reference System and current survey standard using multi-year adjusted locations based on GNSS from the CORS. Surly Straggler vs. other types of steel frames. Benchmarks refer to elevation only and not to geographic position. (e.g. How to tell which packages are held back due to phased updates. Surveyors installed brass or aluminum disks at each reference location. The Add Coordinate Format dialog will appear. proj4js cannot transform nad27 datums to nad83 correctly. The following projection file converts an NAD27 dataset to an NAD83 dataset in Canada: Why y-coordinates may seem 200 meters too large. Especially, this is true when using historical data. However, many of you might have automated your original data layers using NAD27 and continue to do so, primarily because some source data is collected from maps based on NAD27. Not the answer you're looking for? Surveyors connected each monument location using mathematical techniques like triangulation. I have to process millions of records, so an API would likely be too slow. Proj.4 is pretty good, but a perfect example of why I hate to design and execute by committee (with all due respect to the folks overseeing it!). - Conversion of Coordinates in Degrees, Minutes and Seconds to Decimal Degrees. (391326.686 north latitude, 983230.506 west longitude). Why do many companies reject expired SSL certificates as bugs in bug bounties? The challenge is to get points in different datums to align. How to convert WGS84 to NAD27 in pygeodesy? Scope: (null/copy) Approximation for medium and low accuracy applications assuming equality between plate-fixed static and earth-fixed dynamic CRSs, ignoring static/dynamic CRS differences. Thanks for contributing an answer to Geographic Information Systems Stack Exchange! A datum describes the shape of the Earth in mathematical terms. help with formula to convert GPS degrees minutes seconds to decimal degrees. Or is there a QGIS or (better) an OSGeo solution? I know it can be done with GIS programs, but I need a programming function ideally in PHP, but I could convert from any language. How do you ensure that a red herring doesn't violate Chekhov's gun? A horizontal datum provides a frame of reference as a basis for placing specific locations at specific points on the spheroid. Cliff Mugnier. Actually, because of these changes, there is more than one version of NAD83. Browse other questions tagged, Start here for a quick overview of the site, Detailed answers to any questions you might have, Discuss the workings and policies of this site. When you need to accurately enter latitude and longitude coordinates in a GIS, the first step is to give it a datum. Macro/VBA to add text from another cell into current cell when I type a certain value. The UTM system divides the Earth into 60 zones, each 6 of longitude in width. NAD27 to HARN equals 0.15m + 0.05m = 0.20m). - Mintx Aug 4, 2016 at 21:42 To learn more, see our tips on writing great answers. Surveyors could measure any point with a latitude and longitude away from this reference point based on the Clarke Ellipsoid of 1866. Because we created maps using different geodetic datums throughout history, datum transformations are often necessary when using historical data. Is it correct to use "the" before "materials used in making buildings are"? See also: Proper gdaltransform syntax to transform a list of coordinates? Learn more about Stack Overflow the company, and our products. Powered by Invision Community. For example, NAD27, NAD83, and WGS84 are the most common geodetic datums in North America. There is no exact mathematical equation that will convert data built from a surface oriented local datum like NAD27, to an earth centered global datum like NAD83. Unfortunately, NAD83 is not the only datum youll encounter. Your email address will not be published. Then select Nadcon (NGS) from the Type option list. Bessel 1841 was used before Clarke 1866 was adopted because it was based on observations of triangulation arcs of North America. You cannot convert between Old Hawaiian or Alaskan Island and NAD27 because NADCON does not have the necessary information. What sort of strategies would a medieval military use against a fantasy giant? You will get the conversion to result in the Output reference system window. Proj4js returns in datum NAD83 [ -104.998634, 39.74619740515981 ], From http://tagis.dep.wv.gov/convert/ When you combine these measurements, we arrive at a geodetic datum. Geodetic datums form the basis of coordinates of all horizontal positions on Earth. To learn more, see our tips on writing great answers. 10 Topographic Maps From Around the World, Ocean Currents Map: Visualize Our Oceans Movement, Esri JavaScript API Examples: 15 High-Tech Webmaps and Webscenes, 50 Map Projections Types: A Visual Reference Guide [BIG LIST]. You can open imagerywith a world file. And since the beginning of the 19th century, the dimensions of the ellipsoid have been calculated at least 20 different times with considerably different accuracy. I'll investigate the information you have all provided and see if it helps. Not quite sure if I understood you right, but I assume your data got projected on the fly. Farther offshore NAD27 undefined. Terms of Use | Privacy Policy Point databases and shape files can be converted from SPCS to lat-long, which is required to use them in the program. It only takes a minute to sign up. Depending on where you are in North America, NAD27 and NAD83 may differ in tens of meters for horizontal accuracy. Any you already have installed. Where is your data geographically located? Right-click total to add Max, Min, Count, Average. A coordinate transformation is a conversion from a non-projected coordinate system to a coordinate system. Cartisan Total Map Coordinate Converter: Converts from decimal and DDMMSS latitude/longitude to UTM and MGRS, and back again; includes support for 14 datums, including NAD27 and WGS84. I tried using proj4js and proj4php but they cannot do the correct transformation. The best method these days is using distortion models which I believe is used with things like NADCON, http://www.ngs.noaa.gov/TOOLS/Nadcon/Nadcon.html. In areas of sparse geodetic data coverage, NADCON may yield less accurate results but seldom in excess of 1.0 m. Transformations between NAD83 and the States/Regions with High Accuracy Reference Networks (HARN) introduce approximately 0.05 m uncertainty. Nad2Nad may be the simplest to understand (source wise), but it is not the most precise. Answer: EPSG4326 is just the way to identify WGS84 using EPSG. My code is GPL licensed, can I issue a license to have my code be distributed in a specific MIT licensed project? Posted on 1 second ago; June 24, 2022 . I work offshore and dont always have a good internet connection with which to update my apps so I do that from good WiFi before departure. The shift to NAD83 affects the We reference all coordinates to a datum. Disconnect between goals and daily tasksIs it me, or the industry? rev2023.3.3.43278. To be clear, most monuments have not moved. And can you share your projections info? NAD27 and NAD83 -- Significant difference exists between NAD27 and NAD83. Browse other questions tagged, Start here for a quick overview of the site, Detailed answers to any questions you might have, Discuss the workings and policies of this site. To convert into various coordinate formats, we freely offer our Excel template. Similar to NAD 83, it uses the Earths center mass as the coordinate origin. Result is 39.748289809487346 -104.99917122555918. i made the assumption that ellps value unchanged without knowing what extact projection your data is in. Has anyone else used this app and experienced the same thing? Not really. Conversions between NAD27 and NAD83. Go to the menu File>Options Select Advanced At the bottom of the list of options, check the option " Use 1904 date system " Customize the time format Now, let's customize the format of our cell: Open the Format cell dialog box ( Ctrl + 1) Select the option Custom In the Type box, enter this format code exactly as it is displayed below none. Is a list of projection packages, many public domain with source. To convert between feet and metric dimensions they will be converted based on the U.S. Survey foot definition, . This is a PHP-Class for geographic coordinates transformation using proj4 definitions. developers.google.com/maps/documentation/javascript/, How Intuit democratizes AI development across teams through reusability. Using Kolmogorov complexity to measure difficulty of problems? ), Question: Did I actually transform my data points from WGS84 to NAD27? In this case, a datum transformation is necessary. . Get your coordinates in the WGS84 on your display. Why Are Great Circles the Shortest Flight Path? So if you do a transformation with Save As from EPSG:4326 into EPSG:32064, the points of the WGS84 and BLM14 layer should be on top of each other. In case you have coordinates in CSV file somewhere online, you can call this request: Thanks for contributing an answer to Geographic Information Systems Stack Exchange! The early attempts at measuring the ellipsoid used small amounts of data and did not represent the true shape of the Earth. Select a popular spatial reference system from the drop-down list or choose a custom system to enter the functioning EPSG code by yourself. MERCEDES Where To Buy Maps Online: An Insiders Guide, 50 Map Projections Types: A Visual Reference Guide [BIG LIST], Esri JavaScript API Examples: 15 High-Tech Webmaps and Webscenes, 10 Topographic Maps From Around the World. Display as a link instead, When combining data from different users or eras, it is important to transform all information into common geodetic datums. Click Open Map (appears after the end of the conversion) to visualize the converted coordinates on the World map. Asking for help, clarification, or responding to other answers. I wonder if the developer of this app has folded andits no longer available. Copyright 2000-2023 Groundspeak, Inc. DBA Geocaching. Optimal transformation. As the name implies, datum transformations transform your data from one datum to another. North American Datum of 1983 is based on the reference ellipsoid GRS80 which is physically larger than NAD27s Clarke ellipsoid. This difference is known as a datum shift. The NAD27 datum was based on the Clarke Ellipsoid of 1866: The NAD83 datum was based on the Geodetic Reference System (GRS80) Ellipsoid: For any type of work where coordinates need to be consistent with each other, you must use the same geodetic datum. Making statements based on opinion; back them up with references or personal experience. Scientists believe the error is less than 2 centimeters to the center mass. The difference between the phonemes /p/ and /b/ in Japanese. It runs with any browser on any device. after selecting the coordinate conversion button. NAD83 is a geocentric datum (referenced to the center of Earths mass) offset by about 2 meters. When you transform NAD83 and NAD27 geographic coordinates to projected State Plane coordinates, it is the same projection method. - Caleb Pitman Aug 4, 2016 at 21:34 3 You'll want to use some third party tools to do the transform. But given that the datum of the coordinate matches the datum used on the map, you will see no difference in the physical location. Available transformations. Using this app is a fast and easy way to get coordinates in the WGS84 by automatically converting the coordinates of any Spatial Reference System (SRS) or EPSG code. When two datasets are projected into planar coordinates (such as UTM or state plane) and the differences between locations in NAD27 and NAD83 are measured, the y-coordinate is often approximately 200 meters larger than expected. UTM (Universal Transverse Mercator) is a coordinate system that is based on the WGS84 ellipsoid. Over time, surveyors have gathered a massive collection of surface measurements to more reliably estimate the ellipsoid. I've tried right-clicking on my data layer, and choosing an output CRS, but when I load it back and compare, I see no difference. Projected coordinate systems are based on geographic coordinates, which are in turn referenced to a datum. Read More. It consists of a reference ellipsoid, a standard coordinate system, altitude data, and a geoid. This compares to only 26,000 used in the NAD27 datum. It only takes a minute to sign up. READ MORE: Datum Transformations Converting Coordinates from NAD27 to NAD83, Image credit: NADCON North American Datum Conversion Utility, Clarke 1880 was never used in North America. Here is the spatial reference list. Is there a proper earth ground point in this switch box? ", "Transformation steps are from NAD27 to NAD83(HARN) (12) (code 8471) assuming that NAD83(HARN) is equivalent to WGS 84 within the accuracy of the transformation. What is the formula to convert WGS84 coordinates to EPSG 2163? Connect and share knowledge within a single location that is structured and easy to search. To see this for yourself, you can create a coverage of a single arc, running along a meridian from the equator to your point of interest in the coterminous United States. NADCON is the accepted national standard and is the fastest, simplest, and most accurate datum transformation for mapping at scales of 1:200 and smaller. You can also convert coordinates using many other spatial references. To permanent project just do a right click on your data layer in QIGS>Save as>CRS choose the CRS you want. To more clearly see the difference, relative to your Google Maps points (which may be in a different CRS), load the layer, defining it as having a CRS as WGS84 (probably accurate), then right-click on the layer and choose Save As, defining your project CRS of NAD27(BLM14) for the resultant file. This has led to the development of global ellipsoid models such as WGS72, GRS80, and WGS84 (current). http://everest.hunter.cuny.edu/mp/software.html. If so, how close was it? If you have questions about obtaining a more reliable transformation in major urban centers or other areas that are densified, contact ESRI Canada Limited for further details. Enter coordinates, select input and output reference system. (I zoomed in to 47:1. Write a TSQL function to convert NAD83 State Plane (specifically ESRI Projection 102738 http://spatialreference.org/ref/esri/102738/) to WGS84 Lat/Lng so I can, in near real-time, plot the original coordinates on a Google Map. The NAD27 datum was based on the Clarke Ellipsoid of 1866: The NAD83 datum was based on the Geodetic Reference System (GRS80) Ellipsoid: When you transform NAD83 and NAD27 geographic coordinates to projected State Plane coordinates, it is the same projection method. I checked the properties of the layers, and one says +datum=WGS84, while the other says +datum=NAD27. If you are converting to or from state plane, use the NAD27 keyword instead. Preface: I have a set of lat and long data points from Google Maps, which I believe are in WGS84. If you are marking property boundaries, building roads, or planning for coastal inundation scenarios, you must know about and use the correct geodetic datums. In 1880, the Clarke ellipsoid was adopted as a basis for its triangulation computations. The photo shown is a benchmark, not a triangulation station. Scope: (null/copy) Approximation for medium and low accuracy applications assuming equality between plate-fixed static and earth-fixed dynamic CRSs, ignoring static/dynamic CRS differences. You cannot paste images directly. For example, EPSG:4326 and EPSG:4267 are reference codes for WGS84 and NAD27, respectively: will return the corresponding coordinate in NAD27. There is a basic ellipsoidal projection, but then you are supposed to apply offsets from one of several gigantic tables (basically 200 years of empiracly derived and measured data). Makes no sense to me but perhaps it will help you. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. Conversion between NAVD 88 and the commonly used NGVD 29 varies spatially; however, over most of the study area the following conversion can be used: NGVD 29 = NAVD 88 -3.6 feet. A datum defines the radius, inverse flattening, semi-major axis, and semi-minor axis for an ellipsoid. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. Obviously change the reference to suite. NAD27 coordinates are presently used for broadcast authorizations The following projection file converts an NAD27 dataset to an NAD83 dataset: The following keywords (and associated regional coverage) are valid datum names when using the NADCON method for datum transformation. NAD83 corrects some of the distortions from NAD27 over distance by using a more dense set of positions from terrestrial and Doppler satellite data. No one is going to just write some code up for you for free without any effort on your part. The coordinates for benchmark datum points are typically different between geodetic datums. What Is the Difference Between 'Man' And 'Son of Man' in Num 23:19? Canadian Spatial Reference System and Canadian Active Control System with GPS processing. Click on the "Convert" button. JavaScript is disabled. An example is 52 12. Click "Transform" to quickly convert coordinates. The nature of simulating nature: A Q&A with IBM Quantum researcher Dr. Jamie We've added a "Necessary cookies only" option to the cookie consent popup. Unfortunately, NAD27 is not a simple mathmatical formula. Geodesists use a horizontal datum as the model to translate a spheroid/ellipsoid into locations on Earth with latitude and longitude lines. ", "Parameter files are from NAD83 to NAD83(HARN) (12) (code 1485) assuming that NAD83(HARN) is equivalent to WGS 84 within the accuracy of the transformation. I converted NAD27 to NAD83 and put on google maps and it was about the same as WGS84 (maybe 5-8 ft difference). At each station, surveyors collected latitudes and longitude coordinates. Location of data. The tasks of conversion include: WGS84 is intended for global use. The state plane projection will not allow you to use the datum keywords OLD_HAWAIIAN or ALASKAN_ISLAND. However, NAD83 is not geocentric with an offset of about two meters. Surly Straggler vs. other types of steel frames. One of the primary differences is that NAD83 uses an Earth-centered reference, rather than a fixed station in NAD27. As of September 2000, the grids for 44 states and two territories had been published. To learn more, see our tips on writing great answers. Where does this (supposedly) Gibson quote come from? your ~ 50 meters. Please see the popular list below. I had previously found that it sometimes had to be deleted, reloaded to work. Uses NADCON method which expects longitudes positive west; EPSG CRS codes 4267 and 4326 have longitudes positive east. Paste as plain text instead, Copyright 2000-2023 Groundspeak, Inc. DBA Geocaching. The first sentence you wrote perhaps is wrong that the lat long taken from Google maps are not in WGS84 rather they are in NAD27. So convenient!!! Coordinates on a map This page has an example of converting state plane to WGS84: . Thanks! Each works best for a particular region. To transform datums, specify different input and output datums with the DATUM subcommand in a projection file. If you have 'On-the-fly-reprojection' enabled, you should see the difference between WGS84 and NAD27 for the same coordinate pair: But note that you should use EPSG:4267 NAD27 for this, and not EPSG:32064 NAD27-BLM14, which has US feet as units. A minimum curvature-derived surface based on the National Geodetic Reference System determines the transformation of points and has an approximate accuracy of 0.15 to 0.5 meters. http://www.ngs.noaa.gov/cgi-bin/nadcon.prl. Currently, all states have been resurveyed. Shopping at Amazon through the link below helps support the site. Therefore, the Nadcon computed transformations are extrapolations and no accuracy can be stated." Thanks, Rod. Most historical USGS topographic maps and projects by the US Army Corps of Engineers used NAD27 as a reference system. For application in Gulf of Mexico refer to IOGP report 373-26. The link is as follows: http://webapp.geod.nrcan.gc.ca/geod/ Conclusion . For example, surveyors benchmarked approximately 250,000 stations. GDAL/OGR are fairly robust and open source that are made for this. Hi, looks like the Cartisan Total Map Coordinate Converter is no longer available from the website (actually, the whole sites down) Sad to see it disappear. Would anybody have a copy ? Well done. This set of horizontal positions formed the basis for the North American Datum of 1983 (NAD83). If your data is already in NAD27, do not use these options. NAD_1927_To_NAD_1983_6. All input and output linear units are in meters. For example, USGS topographic maps generally were published using a NAD27 datum. Note: Your post will require moderator approval before it will be visible. On the other hand, if we use CORS coordinates data, or the OPUS service, the NAD83 reference frame to which these I've been trying to do this for days. Its important to note that the physical location has not changed. In near offshore regions, results will be less accurate but seldom in excess of 5.0 m. Farther offshore, NAD27 was undefined. The latitudes and longitudes of every other point in North America were based on its direction, angle, and distance away from Meades Ranch. Convert from NAD83 to WGS84 is real fast and easy. Thanks for contributing an answer to Stack Overflow! To add a NAD27 coordinate format in ExpertGPS, click Preferences on the Edit menu, and click on the My Coordinate Formats tab. For example, the State Plane Coordinate System can be referenced to either NAD83 and NAD27 geodetic datums. Also has another version of a converter from degrees/minutes/seconds to decimal degrees and back, similar in output to the one above.Requires that you have macros enabled in your spreadsheet program. What am I doing wrong here in the PlotLegends specification? Why Are Great Circles the Shortest Flight Path? Remarks: Transformation steps are from NAD27 to NAD83 (HARN) (12) (code 8471) assuming that NAD83 (HARN) is equivalent to WGS 84 within the accuracy of the transformation. Did any DOS compatibility layers exist for any UNIX-like systems before DOS started to become outmoded? NGS Coordinate Conversion and Transformation Tool (NCAT) Convert/Transform from: Horizontal+height Select the type of horizontal coordinate: + Leaflet | Sources Esri, DeLorme, HERE, USGS, Intermap, iPC, NRCAN, Esri Japan, METI, Esri China (Hong Kong), Esri (Thailand), MapmyIndia, and the GIS User Community Enter lat-lon in decimal degrees Lat Lon Datum shifts happen because survey measurements improve, there are more of them and methods of geodesy change. Making statements based on opinion; back them up with references or personal experience. Problems with NAD27 included measurement errors and intentional distortions. Input the coordinates in a decimal degrees (DD) format. For example, ArcMap has seven formulas that convert from NAD27 to NAD83. Since 1986, geodesists have made several updates to NAD83. Geodetic datums like the North American Datum 1983 (NAD83) form the basis of coordinates of all horizontal positions for Canada and the United States. Can anyone recommend a good app for multiple datum transformations? Stack Exchange network consists of 181 Q&A communities including Stack Overflow, the largest, most trusted online community for developers to learn, share their knowledge, and build their careers. Coordinates Converter works from all platforms including Windows, Mac, Android, and iOS. The horizontal datums that form the basis of coordinates of all horizontal positions in North America improve. What is the incorrect result for your conversion. Contents of the Free Geography Tools Blog copyright 2007-2018; all rights reserved. Projected coordinate systems are based on geographic coordinates, which are in turn referenced to a datum. After, geodesists developed the more accurate NAD 83, which we still use today. In this case, you would need to perform a datum transformation. Staging Ground Beta 1 Recap, and Reviewers needed for Beta 2, var functionName = function() {} vs function functionName() {}, Reference Guide: What does this symbol mean in PHP? As time went on, the number of stations also grew. Comments are currently closed; feel free to contact me with questions/issues. Adoption of the North American Datum (NAD) of 1983 requires that you store and use map data in a coordinate system based on NAD83. Upload or insert images from URL. When combining data from different users or eras, it is important to transform all information into common geodetic datums.